1,096 research outputs found
Massive Dualities in Six Dimensions
We study compactifications of string theory and M-theory to six dimensions
with background fluxes. The nonzero fluxes lead to additional mass parameters.
We derive the S- and T-duality rules for the corresponding (massive)
supergravity theories. Specifically, we investigate the massive T-duality
between Type IIA superstring theory compactified on K3 with background fluxes
and Type IIB superstring theory compactified on K3. Furthermore, we generalise
to the massive case the 6D 'string-string' S-duality between M-theory on K3 x
S^1 and the Heterotic String on T^4. Whereas in the case of massive T--duality
the mass parameters are in the fundamental representation of the U-duality
group O(4,20) we find that in the case of massive S-duality they are in the
3-index antisymmetric representation. In the latter case the mass parameters
involved extend those of Kaloper and Myers. We apply our duality rules to
massive brane solutions, like the domain wall solutions corresponding to the
mass parameters and find new massive brane solutions. Finally, we discuss the
higher-dimensional interpretation of the dualities and brane solutions.Comment: 28 page
Geometry of all supersymmetric type I backgrounds
We find the geometry of all supersymmetric type I backgrounds by solving the
gravitino and dilatino Killing spinor equations, using the spinorial geometry
technique, in all cases. The solutions of the gravitino Killing spinor equation
are characterized by their isotropy group in Spin(9,1), while the solutions of
the dilatino Killing spinor equation are characterized by their isotropy group
in the subgroup Sigma(P) of Spin(9,1) which preserves the space of parallel
spinors P. Given a solution of the gravitino Killing spinor equation with L
parallel spinors, L = 1,2,3,4,5,6,8, the dilatino Killing spinor equation
allows for solutions with N supersymmetries for any 0 < N =< L. Moreover for L
= 16, we confirm that N = 8,10,12,14,16. We find that in most cases the Bianchi
identities and the field equations of type I backgrounds imply a further
reduction of the holonomy of the supercovariant connection. In addition, we
show that in some cases if the holonomy group of the supercovariant connection
is precisely the isotropy group of the parallel spinors, then all parallel
spinors are Killing and so there are no backgrounds with N < L supersymmetries.Comment: 73 pages. v2: minor changes, references adde
Revealing causal heterogeneity using time series analysis of ambulatory assessments: application to the association between depression and physical activity after myocardial infarction
Objective: Studies in psychosomatic medicine are characterized by analyses that typically compare groups. This nomothetic approach leads to conclusions that apply to the average group member but not necessarily to individual patients. Idiographic studies start at the individual patient and are suitable to study associations that differ between time points or between individuals. We illustrate the advantages of the idiographic approach in analyzing ambulatory assessments, taking the association between depression and physical activity after myocardial infarction as an example. Methods: Five middle-aged men who had myocardial infarction with mild to moderate symptoms of depression were included in this study. Four of these. participants monitored their physical activity and depressive symptoms during a period of 2 to 3 months using a daily self-registration form. The time series of each individual participant were investigated using vector autoregressive modeling, which enables the analysis of temporal dynamics between physical activity and depression. Results: We found causal heterogeneity in the association between depression and physical activity. Participants differed in the predominant direction of effect, which was either from physical activity to depression (n = 1,85 observations, unstandardized effect size = -0.183, p=.03) or from depression to physical activity (n = 2, 65 and 59 observations, unstandardized effect sizes = -0.038 and -0.381, p<.001 and p=.04). Also, the persistency of effects differed among individuals. Conclusions: Vector autoregressive models are suitable in revealing causal heterogeneity and can be easily used to analyze ambulatory assessments. We suggest that these models might bridge the gap between science and clinical practice by translating epidemiological results to individual patients
Inflation by Alignment
Pseudo-Goldstone bosons (pGBs) can provide technically natural inflatons, as
has been comparatively well-explored in the simplest axion examples. Although
inflationary success requires trans-Planckian decay constants, f > Mp, several
mechanisms have been proposed to obtain this, relying on (mis-)alignments
between potential and kinetic energies in multiple-field models. We extend
these mechanisms to a broader class of inflationary models, including in
particular the exponential potentials that arise for pGB potentials based on
noncompact groups (and so which might apply to moduli in an extra-dimensional
setting). The resulting potentials provide natural large-field inflationary
models and can predict a larger primordial tensor signal than is true for
simpler single-field versions of these models. In so doing we provide a unified
treatment of several alignment mechanisms, showing how each emerges as a limit
of the more general setup.Comment: Several references added in update. 7 pages, 4 figure
Reduction of Coxiella burnetii prevalence by vaccination of goats and sheep, the Netherlands
Recently, the number of human Q fever cases in the Netherlands increased dramatically. In response to this increase, dairy goats and dairy sheep were vaccinated against Coxiella burnetii. All pregnant dairy goats and dairy sheep in herds positive for Q fever were culled. We identified the effect of vaccination on bacterial shedding by small ruminants. On the day of culling, samples of uterine fluid, vaginal mucus, and milk were obtained from 957 pregnant animals in 13 herds. Prevalence and bacterial load were reduced in vaccinated animals compared with unvaccinated animals. These effects were most pronounced in animals during their first pregnancy. Results indicate that vaccination may reduce bacterial load in the environment and human exposure to C. burnetii
Classical resolution of singularities in dilaton cosmologies
For models of dilaton-gravity with a possible exponential potential, such as
the tensor-scalar sector of IIA supergravity, we show how cosmological
solutions correspond to trajectories in a 2D Milne space (parametrized by the
dilaton and the scale factor). Cosmological singularities correspond to points
at which a trajectory meets the Milne horizon, but the trajectories can be
smoothly continued through the horizon to an instanton solution of the
Euclidean theory. We find some exact cosmology/instanton solutions that lift to
black holes in one higher dimension. For one such solution, the singularities
of a big crunch to big bang transition mediated by an instanton phase lift to
the black hole and cosmological horizons of de Sitter Schwarzschild spacetimes.Comment: 24 pages, 2 figure
Cosmological D-instantons and Cyclic Universes
For models of gravity coupled to hyperbolic sigma models, such as the
metric-scalar sector of IIB supergravity, we show how smooth trajectories in
the `augmented target space' connect FLRW cosmologies to non-extremal
D-instantons through a cosmological singularity. In particular, we find closed
cyclic universes that undergo an endless sequence of big-bang to big-crunch
cycles separated by instanton `phases'. We also find `big-bounce' universes in
which a collapsing closed universe bounces off its cosmological singularity to
become an open expanding universe.Comment: 21 pages, 4 figures. v2: minor change
Stikstofuitspoeling, -verliezen en -overschotten door bemesting van graslandpercelen in het stroomgebied van de Beerze en de Reusel
The Relation Between Children’s Perceived Group Climate and Therapeutic Alliance with Their Mentor in Residential Care: A Prospective Study
Cross-Comparison of Climate Change adaptation Strategies Across Large River Basins in Europe, Africa and Asia
A cross-comparison of climate change adaptation strategies across regions was performed, considering six large river basins as case study areas. Three of the basins, namely the Elbe, Guadiana, and Rhine, are located in Europe, the Nile Equatorial Lakes region and the Orange basin are in Africa, and the Amudarya basin is in Central Asia. The evaluation was based mainly on the opinions of policy makers and water management experts in the river basins. The adaptation strategies were evaluated considering the following issues: expected climate change, expected climate change impacts, drivers for development of adaptation strategy, barriers for adaptation, state of the implementation of a range of water management measures, and status of adaptation strategy implementation. The analysis of responses and cross-comparison were performed with rating the responses where possible. According to the expert opinions, there is an understanding in all six regions that climate change is happening. Different climate change impacts are expected in the basins, whereas decreasing annual water availability, and increasing frequency and intensity of droughts (and to a lesser extent floods) are expected in all of them. According to the responses, the two most important drivers for development of adaptation strategy are: climate-related disasters, and national and international policies. The following most important barriers for adaptation to climate change were identified by responders: spatial and temporal uncertainties in climate projections, lack of adequate financial resources, and lack of horizontal cooperation. The evaluated water resources management measures are on a relatively high level in the Elbe and Rhine basins, followed by the Orange and Guadiana. It is lower in the Amudarya basin, and the lowest in the NEL region, where many measures are only at the planning stage. Regarding the level of adaptation strategy implementation, it can be concluded that the adaptation to climate change has started in all basins, but progresses rather slowl
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